This invention is related to a heat engine and particularly to an improved Stirling cycle engine incorporating a mechanism for modulating the displacement of the engine.
In order that a Stirling engine meet the output requirements demanded for a particular operating condition, some means of power modulation is required. One approach is through adjusting the swept volume or displacement of the reciprocating pistons of the machine. The Assignees of the present invention have developed numerous approaches toward providing such modulation adjustment. In the Stirling engine of the type described in this specification, modulation adjustment is achieved by changing the angle which the swashplate forms from its axis of rotation. As the swashplate face surfaces approach a plane perpendicular to its axis of rotation, the swept volume of the pistons decrease. Conversely, when the swashplate face surfaces are inclined from a plane perpendicular to its rotational axis, the swept volume of the pistons increase.
The Assignees of the present application have incorporated various mechanical, electrical and hydraulic systems for causing the swashplate angle to be varied in a desired manner. One series of devices provides hydraulically actuated swashplate adjustment as described by U.S. Pat. No. 4,532,855. Various electrically driven actuators have also been described by the Assignee, including those described in U.S. Pat. Nos. 4,994,004; 5,611,201; and 5,836,846. Although the devices described by those previously referenced patents are viable designs, there is a continuing need to provide such adjustment systems which have the features of simplicity, rapid transient response, and reliability. This invention is aimed at achieving those desirable features. This invention further addresses the need to provide a measure of swashplate angle, needed as part of a variable swashplate control system.
In accordance with the present invention, a swashplate actuator system is described incorporating a hydraulic actuation system. The mechanism uses hydraulic pressure to move a rotary vane for providing swashplate angle adjustments.
The present invention further provides two approaches toward measuring swashplate angle, each using one or more proximity probes interacting with portions of the rotating driveshaft or the reciprocating motion of the cross heads of the engine.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.